The 3rd Generation Partnership Project (3GPP for short) Evolved Packet System (EPS for short) is comprised of the Evolved Universal Terrestrial Radio Access Network (E-UTRAN for short), the Mobility Management Entity (MME for short), the Serving Gateway (S-GW), the Packet Data Network Gateway (the P-GW or PDN GW for short), the Home Subscriber Server (the HSS for short), the 3GPP Authentication, Authorization and Accounting server (AAA for short) server, the Policy and Charging Rules Function (PCRF for short) entity and other supporting nodes. FIG. 1 is a diagram of architecture of a related EPS system. As shown in the figures, the MME is responsible for control plane related works such as mobility management, processing of non access stratum signaling, the management of user mobility management context; the S-GW is an access gateway device which is connected to the E-UTRAN, transfers data between the E-UTRAN and the P-GW, and is responsible for buffering paging wait data.
The P-GW is a border gateway between the EPS and a Packet Data Network (PDN for short) network, and is responsible for functions such as access of the PDN and data forwarding between the EPS and the PDN etc. The P-GW is responsible for allocating an IP address to the terminal, and is also a mobility anchor of the terminal at the same time. No matter where the terminal moves, a data packet (an IP packet) received and transmitted between the terminal and the outside always needs to be forwarded via the P-GW. Such mobility management scheme will result in problem of roundabout routing recognized in the industry. That is, when a distance between the terminal and a communication Correspondent Node (CN) thereof is very close and the terminal is far from the anchor of the terminal (P-GW), the data packet received and transmitted between the terminal and the CN also must be routed via the anchor.
The industry currently proposes a series of new mobility management technologies based on a user identity and location separation technology, which can solve the above problem of routing roundabout. FIG. 2 illustrates the architecture of an identity and location separation based network. In the architecture of the network, the network is divided into access networks and a backbone network without overlap in a topology, wherein, the access networks are located at the edge of the backbone network, and are responsible for the access of all terminals, and the backbone network is responsible for routing and forwarding of data packet between access terminals. An identity identifier of a terminal user is represented as Access Identifier (AID). No matter in where the terminal accesses the network, and no matter how the terminal moves in the network, the access identifier remains unchanged; and the location identifier of the terminal is represented as Routing Identifier (RID), and is allocated by the network for use in the backbone network. It should be illustrated that different architecture based on identity and location separation may have different names, but the substances thereof are the same. In addition, the terminal may be one or more of a mobile terminal, a fixed terminal, and a nomadic terminal, such as a mobile phone, a fixed-line telephone, a computer and a server etc.
In the architecture of the network illustrated in FIG. 2, the access network is used to provide a layer-two (a physical layer and a link layer) access means for the terminal and maintain a physical access link between the terminal and an Access Service Router (ASR). Primary network elements of the backbone network include an ASR, an Identity Location Register (ILR) and a Common Router (CR).
The ASR is a border router of the backbone network, and its function is to allocate a RID to the terminal, locally maintain a mapping relationship between the AID and the RID of the terminal, and update the RID of the terminal stored by the ILR; and when a data packet is transmitted from the terminal to a CN of the terminal, the RID of the CN is inquired based on the AID of the CN from the ILR, and the data packet is forwarded to the CN based on the RID of the CN etc. The terminal needs to access to the backbone network via the ASR, and the RID allocated by the above ASR to the terminal includes address information of the ASR, or an address pointing to the ASR. After the ASR receives the data packet transmitted by the terminal to the CN, the RID of the terminal and the RID of the CN are used to perform tunneling encapsulation on the data packet and transmit it to the CN; and when the ASR of the CN receives the data packet after being performed with the tunneling encapsulation, the RID tunneling encapsulation of an outer layer is stripped, and the data packet is then transmitted to the CN. The CR is a general router widely deployed in the backbone network, for example, a core router therein, and its function is to select a route according to the RID in the data packet, and forward a data packet with the RID as a destination address. The ILR is used to store and maintain mapping information from the identity identifier to the location identifier of the terminal, i.e., a mapping relationship between the AID and the RID of the terminal, and process the registration, deregistration and inquiry of the terminal location. It should be pointed out that the backbone network may further comprise an Internet Service Router (ISR) and which is an interface to a traditional IP network, an ASR and an ILR for achieving internet interconnection between an identity and location separation network and a traditional IP network.
In order to be compatible with an existing IP network, the above AID is generally represented by selecting a format of an IP address for use, for transparent support for the application program and terminal devices, i.e., the socket of the application program is still connected to the IP address, and needs not to be changed. But in an actual semantics, the IP address as the AID merely expresses identity information of one terminal, and does not express the location information of the terminal, that is, although the AID takes a form of an IP address, it is not a routable IP address in a traditional sense. As described above, the RID is used to express the location information of the terminal. In order to achieve normal forwarding of a packet, when the ASR receives a data packet transmitted by a terminal to a CN, the ASR needs to be aware of the RID of the CN and perform tunneling encapsulation on the data packet. The data packet after being performed with tunneling encapsulation possesses two IP headers, a source address of an outer IP header is a RID of the terminal, and a destination address is a RID of the CN; a source address of an inner IP header is an AID of the terminal, and a destination address is an AID of the CN. Thus, the interconnection between the terminal and the CN can be achieved.
As described above, the mobility related method based on an identity and location separation technology depends on tunneling encapsulation on the data packet, and needs to perform an IP packet encapsulation again on the data packet transmitted by the terminal to the CN, thus increasing a length of the header of the packet and resulting in overhead increase of the backbone network. Particularly when such mobility management technology is applied in the above EPS network, since the EPS itself supports and also prefers to use the Internet Protocol Version 6 (IPv6), such use of the above tunneling encapsulation mechanism will further aggravate resource consumption of the backbone network and increase the cost of the backbone network.